a) (3x+1)²+3x(5x-2)
=9x²+6x+1+15x²-6x
=24x²+1
b) (3y-6)(3y+6)+(6y-4)²
=9y²-36+36y²-48y+16
=45y²-48y-20
c) (-8x+5)²-(2x-10)²
=64x²-80x+25-(4x²-40x+100)
=64x²-80x+25-4x²+40x-100
=60x²-40x-75
d) (6x-13)(8x+3)+y(5y+8)
=48x²+18x-104x-39+5y²+8y
=48x²+5y²-86x+8y-39
e) (y-6)²+(5y-1)(5y+1)
=y²-12y+36+25y²-1
=26y²-12y+35
f) -7(2x+2)²-(x-2)²
=-7(4x²+8x+4)-(x²-4x+4)
=-28x²-56x-28-x²+4x-4
=-29x²-52x-32
